In order to effectively and efficiently make use of available storage space, storage systems comprised of a number of movable storage units such as bookshelves are often utilized. In these systems access is typically provided to less than all of the storage units at any one time. Thus, the storage units are movable in order to provide access to different selected ones of the units.
Such storage systems are disclosed, for example, in Ruoss U.S. Pat. No. 3,575,298; Staller et al. U.S. Pat. No. 3,640,595; Mastronardi et al. U.S. Pat. No. 3,957,322; Tucker et al. U.S. Pat. No. 3,957,323; and Naito et al. U.S. Pat. No. 4,033,649. Each of these patents discloses movable storage apparatus in which various storage units are reciprocally movable to selectively separate adjacent storage units to establish an aisle or access path between those units. The units may be moved to selectively provide access between different pairs of spaced apart units.
In these apparatus, as distinguished from stationary shelving, access is typically provided only between one pair of units. The remaining units abut or are positioned immediately next to the next adjacent units. As a result, access to those storage units is precluded. Thus, in order to obtain access to a pair of units other than the pair which have previously been separated to provide an access path, selected units are moved to close the previously separated units and to separate a different pair and provide access thereto.
As is shown in the above cited patents, such apparatus incorporate one or more electrical drive motors for moving the units to obtain separation between two selected storage units. This is initiated in response to operation of manually operated switches. In order to achieve this type of operation, it is necessary to determine when units approach the next adjacent unit in order to terminate movement thereof and ultimately stop all the movement when separation between the selected units has been achieved.
In these systems, the necessary movement and control requires large numbers of switches and some very complicated wiring and relay controls.
For example, in the Staller et al. U.S. Pat. No. 3,640,595, each of the units incorporates an electric motor, which when energized, causes the unit with which it is associated to move in one of two directions. In order to operate the motor in the proper direction, a large number of hard wired circuits and control switches are provided and very complicated wiring systems are utilized. As a result, as each unit is moved in a selected direction, switches are sensed and operated in order to allow the units to be moved, and to terminate movement and de-energize the motor for that unit as it approaches an adjacent unit.
If it is desired to move a unit towards another unit from which it is separated, a limit switch is closed and a circuit completed through that closed switch to a drive motor. At the same time, other switches must be operated to insure the proper direction of operation. As the movement of that unit begins, the circuitry must preclude energization of the motor in the wrong direction and, furthermore, interconnects with the the next adjacent unit so it may be operated in response to the closure of the appropriate switches resulting from the separation of the first unit from the second to be moved. As each unit approaches the adjacent unit in the direction of movement, limit switches in the motor circuit are opened in order to de-energize the motor for that unit.
Thus, a large number of mechanical switches are required in the motor circuit, and the large number of relays used adds additional expense and complexity to the control system for that unit and severely limits the flexibility of operation because of the extensive wiring and switching which is required.
Tucker et al., U.S. Pat. No. 3,957,323 is quite similar to the previously discussed Staller et al. patent in that a large number of switches and relays are utilized in the motor circuits for controlling and operating each unit in the necessary direction by energizing and de-energizing the motor at the proper time. In the very complicated Tucker system there is extensive use of relay circuits which are operated in order to initiate movement, to control other relay circuits, and to return the control circuit to a quiescent or idle state after movement of the shelves and storage units has been terminated.
The Naito et al. U.S. Pat. No. 4,033,649, discloses another highly complex electrical wiring circuit in which a number of selection switches are connected in the various motor circuits to initiate operation of the motors and move the various storage units from one position to another. The complexity of the disclosed control circuits, as shown in the patent drawing, including the large number of switches and relays required, presents the same problem as discussed above in terms of limited flexibility, operational problems, and reliability.
In each of the patents discussed above, movement of the various units is initiated one after the other in response to switches in the various units being actuated by a gap created between that unit and the next adjacent one as a result of the movement of one of the units. The storage apparatus disclosed in Ruoss U.S. Pat. No. 3,575,298 and Mastronardi et al. U.S. Pat. No. 3,957,322 are similar in that extensive and complex wiring systems with numerous switches and relays are provided. These switches are necessary in order to effect the desired movement of different storage units in different directions as a function of the existing position of the units and their desired final position.
The patents briefly discussed above are typical of the techniques disclosed in the prior art for attempting to selectively move and shift storage units such as movable bookshelves from one position in which a first pair of units are separated to another position in which another pair of units are separated to selectively provide access to different portions of the storage assembly. The complexity of such systems and the necessity for providing extensive and complicated circuitry limits the flexibility and reliability of those systems, and requires extensive amounts of high voltage wiring in order to selectively control operation of one or more reversible motors. All of this tends to inhibit the use of such systems and increase their cost.